机械工程英语第二版第二部分完整翻译(叶邦彦、陈统坚主编)(2)

program is fed into the control unit, which directs the processing equipment accordingly.

三部分的基本关系，由图2.1 所示。程序输入到控制单元由送入的程序来引导加工设备控制。

The program of instructions is the detailed step-by-step commands that direct the processing equipment. In its most common form, the commands refer to positions of machine tool spindle with respect to the worktable on which the part is fixture. More advanced instructions include selection of spindle speeds, cutting tools, and other functions. The program is coded on a suitable medium for submission to the machine control unit. The most common medium in sue over the last several decades has been 1-in.-wide punched tape. Because of the widespread sue of the punched tape, NC is sometimes called “tape control”. However, this is a misnomer in modern usage of numerical control. Coming into use more recently have been magnetic tape cassettes and floppy diskettes.

指导程序是一步步详细的指导加工设备的指令。通常指令把主轴上刀具相对于安装工具的工作台定位。更多先进的说明包括主轴的转速，加工工具的选择及其功能。程序刻在合适的介质中，提交到机器控制单元中，在过去几十年中，最常用的介质是一英寸宽的打孔纸带。由于打孔纸带的广泛使用，NC 有时也叫纸带控制，然而这是现代数控使用的误称。现在进入使用更多的是磁带和软盘。 The machine control unit (MCU) consists of the electronics and control hardware that read and interpret the program of instruction and convert it into mechanical actions of the machine tool or other processing equipment.

机器控制单元（MUC）由电子和控制硬件组成，机器控制单元可以读出和执行指令程序，可以自动改变加工工具和其他加工设备。

The processing equipment is the third basic component of an NC system. It is the component that performs useful work. In the most common example of numerical control, one that performs machining operations, the processing equipment consists of the worktable and spindle as well as the motors and controls needed to drive them.

执行单元是数控系统的第三基础部分，执行原件是有效执行工作的原件，最常见的数控例子其中的一个加工操作，加工设备由工作台和主轴组成，就像用电动机来驱动一样。加工设备由控制单元来驱动控制系统的类型。 Types of Control Systems控制系统的类型

There are two basic types of control systems in numerical control: point-to-point and contouring. In the point-to-point system, also called positioning, each axis of the machine is driven separately by leadscrews and, depending on the type of operation, at different velocities.

数控有2种基本类型，点对点式和轮廓式控制，点对点式控制也称定位控制，每个轴都是通过丝杠单独驱动，根据加工类型不同，加工速度也不一样。The machine moves initially at maximum velocity in order to reduce nonproductive time but decelerates as the tool reaches its numerically defined position.

机器开始以最大速度运行来减少非加工时间，但当他达到数据定义的位置时，机器开始减速。

Thus in an operation such as drilling or punching, the positioning and cutting take

place sequentially.

因此在一个操作中，如钻或冲孔操作先定位再加工。

After the hole is drilled of punched, the tool retracts, moves rapidly to another position, and repeats the operation.

在钻或冲孔之后，迅速收起工具移动到另一个位置重复此操作。

The path followed from one position to another is important in only one aspect: The time required should be minimized for efficiency.

从一个位置移到另一个位置是非常重要的，要遵循一个原则，从效率上考虑只要时间最短即可。

Point-to –point systems are used mainly in drilling, punching, and straight milling operations.

点对点系统主要用于钻，冲孔，直铣操作中。

In the contouring system, also known as the continuous path system, positioning and cutting operations are both along controlled paths but at different velocities. Because the tool cuts as it travels along a prescribed path, accurate control and synchronization of velocities and movements are important. 轮廓式也就是连续路径式系统，定位和切削同时按不同速度来控制，由于刀具在指定路线运动同时切削，因此速度和运动的同步控制是非常重要的。 The contouring system is used on lathes, milling machines, grinders, welding machinery, and machining centers.

轮廓式系统常用于车床铣床磨床焊接设备和加工中心。

Movement along the path, or interpolation, occurs incrementally, by one of several basic methods. In all contouring interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tool wear during machining, can be made in the NC program. 沿着路径的运动或以增量差补是几个基本方式的一个，在所有的差补中，要控制刀具的回转中心定位，补偿可以以不同直径及刀具磨损，在数控程序中进行改写。 There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with a contouring-type NC system. They include: .Linear interpolation .Circular interpolation .Helical interpolation .Parabolic interpolation .Cubic interpolation

有一些已形成差补方案来处理数控系统中连续路径和加工系统产生的问题包括： 1.线性差补；2.圆弧差补；3.螺旋线差补；4.抛物线差补；5.立体差补

Each of these interpolation procedures permits the programmer (or operator) to generate machine instructions for linear or curvilinear paths, using a relatively few input parameters. The interpolation module in the MCU performs the calculations and directs the tool along the path.

每一种差补程序都允许程序源产生加工指令，适用于相对少的输入参数的直线或曲线路径。储存在数控单元中的模块预算指引工具沿计算出的路径运动。 Linear interpolation is the most basic and is used when a straight-line path is to be

generated in continuous-path NC.

线性差补是最基本的差补方法，用于连续路径的数控系统中。

Two-axis and three-axis linear interpolation routines are sometimes distinguished in practice, but conceptually they are the same. The programmer is required to specify the beginning point and end point of the straight line, and the feed rate that is to be followed along the straight line. The interpolator computes the feed rates for each of the two (or three) axes in order to achieve the specified feed rate.

两轴和三轴线性差补路线在实际中有时会分辨出的，但在概念上他们是一样的，程序源要明确指定直线的起点和缺点及沿直线的进给率。差补需计算两轴或三轴的进给速率以达到设定的进给速度。

Linear interpolation for creating a circular path would be quite inappropriate because the programmer would be required to specify the line segments and their respective end points that are to be used to approximate the circle.

线性差补用来差补圆是不合适的因为程序源需要明确指定线段部分（线段数量）和各自的终点来大约模拟圆弧。

Circular interpolation schemes have been developed that permit the programming of a path consisting of a circular arc by specifying the following parameters of the arc: the coordinates of its end points, the coordinates of its centre, its radius, and the direction of the cutter along the arc.

圆弧差补法已形成他允许程序编程的路径，使用圆弧只要给定以下参数，圆弧终点坐标，圆心坐标，半径和刀具沿圆弧路径的走刀方向。

The tool path that is created consists of a series of straight-line segments, but the segments are calculated by the interpolation module rather than the programmer. The cutter is directed to move along each line segment one by in order to generate the smooth circular path. A limitation of circular interpolation is that the plane in which the circular arc exists must be a plane defined by two axes of the NC system. 圆弧差补也是由许多小的直线段来实现的，但这些小线段的参数由差补模块来计算出来的，而不是程序员设定的。切削是沿着每一小线段一个一个的进行以产生光滑曲线路径。圆弧差补的局限性是圆弧路径所在平面是由数控系统中两轴所决定的平面。

Helical interpolation combines the circular interpolation scheme for two axes

described above with linear movement of a third axis. This permits the definition of a helical path in three-dimensional space.

螺旋线差补结合了环形差补两轴在第三轴上做线性运动这样来定义空间三维螺旋路径。

Parabolic and cubic interpolation routines are used to provide approximations of free-form curves using higher-order equations. They generally require considerable computational power and are not as common as linear and circular interpolation. Their applications are concentrated in the automobile industry for fabricating dies for car body panels styled with free-form designs that cannot accurately and conveniently be approximated by combining linear and circular interpolations. 抛物线差补和立方差补法通过高次高程来实现自由曲线。这通常需要有强的计算能力，正因如此，他不如直线差补和环形差补常见。他们主要用于汽车工业中具有自由风格的车身面，而这是线性差补和圆弧差补不能精确容易得到的。

The most common application of numerical control is for machine tool control. This was the first application of NC and is today the most important commercially. In this section we discuss the machine tool applications of NC with emphasis on metal machining.

数控技术运用于数控机床，这是数控的主要应用。现在主要用于商业。我们仍讨论数控系统特别是金属数控车床。

Machine Tool Technology for NC数控车床技术

Each of the five machining processes is carried out on a machine tool designed to perform that process.

五种加工程序的每种加工过程都可以在设计的专门车床上来实现加工。

Turning is performed on a lathe, drilling is done on a drill press, milling on a milling machine, and so on. There are several different types of grinding operations with a corresponding variety of machines to perform them. Numerical control machine tools have been designed for nearly all of the machining processes.

在车床上车削，在钻床上钻，在铣床上加工。有几种类型的磨削方法也要有相应种类的磨床。被设计的数控磨床可以进行下列加工 The list includes: Drill presses

Milling machines, vertical spindle and horizontal spindle Turning machines, both horizontal axis and vertical axis Horizontal and vertical boring mills Profiling and contouring mills

Surface grinders and cylindrical grinders

包括：1.钻加工；2.铣床,立式和卧式主轴；3.车床,卧式主轴和立式主轴；4.卧式和立式镗床；5.仿形铣床；6.平面磨和圆柱磨

In addition to the machining process, NC machine tools have also been developed for other metalworking processes.

除了上述几种机械加工方法，数控机床可用于其他金属加工过程. These machines include:

Punch presses for sheet metal hole punching Presses for sheet metal bending

包括：用于薄片板的金属板上冲孔的冲压机，用于薄片金属弯曲的折弯机。 The introduction of numerical control has had a pronounced influence on the design and operation of machine tools. One of the effects of NC has been that the

proportion of time spent by the machine cutting metal under program control is significantly greater than with manually operated machines.

数控技术的介入到机加工对机床的设计和运用有着显著的影响。数控影响之一在程序控制下切削金属的时间与传统手动机床大得多

This causes certain components, such as the spindle, drive gears, and feed screws, to wear more rapidly. These components must be designed to last longer on NC machines.

所以对于一些零件如主轴驱动主轴丝杠磨损更快，这些零件要设计成持续时间长的。

Second, the addition of the electronic control unit has increased the cost of the

machine, therefore requiring higher equipment utilization.

第二，增加电子控制单元后设备成本也随之增加，因此需要更高的利用率。 Instead of running the machine on only one shift, which was the convention with manually operated machines, NC machines are often operated two or even three shifts to obtain the required payback.

取代传统手工操作的一班制，数控机床通常采用两班或三班制来获得更多的回报。

Also, the NC machines are designed to reduce the time consumed by the

non-processing elements in the operation cycle, such as loading and unloading the workpart, and changing tools.

数控机床的设计中减少了非操作过程的时间如装卸工件和换刀时间。

Third, the increasing cost of labor has altered the relative roles of the operator and the machine tool. Consider the role of the human operator. Instead of being the

highly skilled worker who controlled every aspect of the part production, the tasks of the operator have been reduced to part loading and unloading, tool changing, chip clearing, and the like.

第三，增加的劳动成本由人工成本变为设备成本。考虑到人工操作的角色，角色由技术熟练的工人控制，工件生产的每一个过程变为只控制装卸换刀和清除碎屑和类似的操作，

In this way, one operator can often run two or three automatic machines. The role and functions of the machine tool have also changed. NC machines are designed to be highly automatic and capable of combining several operations in one setup that formerly required several different machines.

这样一个工人可以同时操作两台或三台车床，机床的角色和功能也改变了。数控需要设计成高度自动化具有需要在不同车床加工几种操作联合在一起一定加工的能力，

These changes are best exemplified by a new type of machine that did not exist prior to the advent and development of numerical control: the machining centre. 这些变化是通过一种新型车床在数控技术存在之前是不存在的，他丰富了数控加工中心

The machining centre, developed in the late 1950s, is a machine tool capable of

performing several different machining operations on a workpart in one setup under program control. The machining centre is capable of milling, drilling, reaming,

tapping, boring, facing, and similar operations. In addition, the features that typically characterize the NC machining centre include the following:

加工中心是在20 世纪50 年代发展起来的具有在程序控制下在一个工件上一次裝夹完成几种不同的加工能力的机床。加工中心能完成铣，钻，铰屑，攻丝，镗，车端面及一些类似机加工工作。另外数控加工中心的典型特征包括以下方面： Automatic tool-changing capability. A variety of machining operations means that a variety of tools is required. The tools are contained on the machine in a tool

magazine or drum. When a tool needs to be changed, the tool drum rotates to the proper position, and an automatic tool changing mechanism, operating under program control, exchanges the tool in the spindle and the tool in the drum.

自动换刀能力: 多种机加工工作意味着需要多种刀具。刀具贝安装在刀库或多刀

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